Open Access

Polymer membranes are critical functional components in proton-exchange membrane water electrolyzers (PEMWEs), where they simultaneously enable ionic transport, separate reactive gases, and Sustain mechanical loads. Despite their central role, membrane failure remains a key limitation for System reliability and safety, driven by the complex interaction of electrochemical reactions, two-phase flow, transport processes, and material degradation due to mechanical, chemical, and thermal loads. In particular, gas-liquid flow regimes in catalyst layers, porous transport layers, and flow channels strongly influence local pressure, temperature, and concentrations at the membrane interface. These impact the membrane’s hydration conditions, inducing heterogeneous swelling, stress concentrations, and Membrane thinning, which accelerates the aging process. This contribution presents a multiphysics modeling framework for the simulation-based investigation of membrane degradation and failure mechanisms in PEMWEs, synthesizing ideas from previous works into a novel integrated modeling approach. Two-phase flow in the adjacent porous and free-flow regions is described using porous-media formulations and phase-field computational fluid dynamics, resolving gas generation, saturation, and pressure fields under different operating conditions. The resulting interface quantities are coupled to a porous-mixture-based finite strain membrane model that accounts for hydration-dependent transport and swelling-induced deformation. Damage or failure indicators are introduced to capture the onset of critical membrane degradation driven by cyclic loading, dehydration, or pressure fluctuations. This modeling concept enables systematic analysis of how operating conditions and flow regimes, including annular or mist-like patterns, contribute to membrane stress and failure risk. The Framework provides a foundation for predictive lifetime assessment and supports the design of more durable and safer electrolyzer systems.

Digital transfer documents that are machine-readable – and ideally, machine-interpretable – offer a promising route for automating processes that require seamless digital data transmission. To ensure interoperability on both, the issuing and receiving sides, it is crucial to adopt harmonized solutions when transitioning from analogue-based to fully digital calibration certificates. This shift necessitates that the metrological communities establish agreed-upon best practices and guidelines for implementing these digital assets. This article describes how the specification of data formats and terminology for digital calibration certificates facilitates machine-interpretability and automation in metrological traceability and how the German Calibration Service (DKD) elaborates and reveals these harmonized solutions in comprehensive committee activities. With the establishment of these specifications, quality assurance in measurement technology will finally become more fast, easy, safe and affordable.

We present a fully coupled, patient-specific 3D–0D computational framework for hearts supported with left ventricular assist devices (LVAD) that enables controlled in silico experimentation. The approach monolithically integrates three-dimensional CFD of the left ventricle (LV), left atrium (LA), aortic root, and LVAD cannulae with a closed-loop 0D lumped parameter network of the full circulation. Mitral and aortic valve dynamics are governed by transvalvular pressure and flow with patient-specific regurgitant orifice areas, and the LVAD is represented via a pressure–flow (H–Q) relation. This manuscript provides the complete mathematical formulation, coupling strategy, and parameterization required to build a reproducible pipeline from dynamic CT, 2D transthoracic echocardiography, and right heart catheterization. This methodology is demonstrated in a patient under long-term support of LVAD and concomitant mitral and aortic regurgitation. The personalized, fully coupled 3D–0D models reproduced available clinical targets with a mean error of 8.6%, enabling controlled in silico interrogation of valve repair strategies. In the patient-specific state, simulated mitral and aortic regurgitant volumes were 6.6 and 6.5 mL per cycle, yielding a forward cardiac output of 3.16 L/min despite an LVAD flow of 3.7 L/min. In silico isolated mitral valve (MV) repair, isolated aortic valve (AV) repair, and combined MV+AV repair increased forward output to 3.41, 3.33, and 3.55 L/min, respectively; however, aortic valve opening and increased aortic pressure pulsatility (up to 38.9 vs. 13.5 mmHg) were observed only when MV repair was involved. These left-sided improvements propagated through the cardiopulmonary circulation, reducing pulmonary pressures and right ventricular loading, with the largest benefit observed following combined repair. We show that the modeling platform presented provides a powerful means to study mechanical circulatory support, enabling patient-specific evaluation of surgical interventions in patients with LVAD and delivering quantitative insight into clinically important metrics—such as aortic pulsatility, RV afterload, and chamber-level flow patterns.

Adhesive interactions play a crucial role in collisions involving soft and compliant materials, yet classical impact models based on the Johnson–Kendall–Roberts (JKR) theory often underestimate experimentally observed energy losses. Motivated by evidence of adhesion hysteresis, we develop a model for the collision of an elastic sphere with an elastic half-space in which the loading and unloading stages are governed by different contact mechanisms. The indentation phase is described by non-adhesive Hertzian contact, whereas the rebound phase follows the adhesive JKR theory. This asymmetric Hertz–JKR formulation captures the additional Dissipation associated with secondary adhesion hysteresis. Universal expressions for the coefficient of restitution and the relative energy loss are obtained in dimensionless form as functions of a single adhesion parameter. These relationships constitute master curves that are independent of impact velocity, particle size, elastic properties, and work of adhesion. The model predicts significantly greater energy dissipation than the classical JKR approach across the entire range of adhesion parameters and yields a lower critical threshold for particle sticking after impact. The results provide a realistic framework for describing adhesive particle collisions in granular media, powders, aerosols, and other particulate systems.

A large explosion occurred at an oil refinery after a desulfurization reactor cracked, releasing hot, pressurized gasoline. The resulting explosions and fire caused extensive damage and injured some employees. A 1.4 m crack adjacent to a weld seam at a reactor support bracket caused the release. The reactor shell exhibited distinctive circumferential bulging. The reactor was erected using mild steel. All material properties of the reactor shell complied with the regulations in effect at that time. Fractographic analysis of the main crack and smaller ones at the other support brackets revealed stepwise ductile fracture resulting from static loading. All well-known failure mechanisms for pressure vessel burst had proven wrong: overpressure, pressure cycles, overtemperature, creep, corrosion, external (cyclic) mechanical loads… Due to small spherical indentations on the inside of the reactor shell, a completely new failure mechanism was established and investigated: During service, the reactor was partially filled with ceramic ball grading and catalyst. Gasoline was processed at 150–250 °C and ∼ 24 bar. Each of the reactor’s ∼ 20 operating cycles ran for several months until the catalyst was spent, after which the reactor was cooled, depressurized, emptied, and refilled. Upon heating, the thermal expansion of the steel shell (∼3 times greater than ceramic) created gaps that were filled as ceramic balls settled. During operation, the catalyst degraded and agglomerated with the ceramic balls, forming a rigid mass. Upon cooling, the rigid mass resisted the vessel’s thermal contraction, inducing circumferential tensile stresses and plastic deformation, resulting in permanent bulging of the vessel. Charpy impact energy near the welds was significantly reduced, attributed to thermal and strain aging in the bulged region. Progressive embrittlement and increasing plastic strain led to crack initiation and incremental ductile crack propagation at the support bracket welds over successive cycles. The fracture features were reproduced in laboratory tests at 200 °C. FEA analysis confirmed the proposed mechanism. Two identical vessels showed similar damage but had not yet failed. To prevent future damage in pressure vessels, this new failure mechanism needs to be incorporated into design, operating and inspection codes for pressure vessels possibly/partially filled with solids.